1. Field of the Invention
The present invention is directed to a by-pass or attenuator device and more specifically to a miniaturized ceramic device intended to attenuate noise at two discrete frequencies. Without limitation, a particular utility of the device is as a noise attenuator in so-called dual mode cellular phones having both a digital and an analog output. In devices of this sort, where transmission is effected simultaneously on two discrete frequencies, it is desirable to minimize the "noise" generated by each of the two frequencies.
2. Prior Art
Conventional practice in respect of the recently developed dual mode cellular phones is to provide discrete LC networks tailored to attenuate (shunt to ground) the noise generated in the respective digital and analog transmission circuits. With the current trend to miniaturization, the requirement of utilizing discrete components to be attached to the motherboard is undesirable in that the multiple components occupy precious "geography".
Perhaps, more importantly, in the ultra high frequencies involved in cellular technology (900 MHz for analog transmissions and 1.9 GHz for digital transmissions) the inclusion of lead paths to the respective separate components results in a great variation in inductances, since the lead paths themselves function as inductors.
The references noted below were obtained as a result of a prior art search in respect of the instant invention.
U.S. Pat. No. 5,430,601 discloses a MLC which includes a resistance connection.
U.S. Pat. No. 5,170,317 discloses a MLC which includes, in addition to the conventional electrodes, a "correction" electrode which is narrower than the major electrodes to enable the provision of a capacitor having a precise value.
U.S. Pat. No. 4,758,922 discloses a U-shaped "strip line" which functions as a resonance element (capacitor) having ground plane layers and intervening dielectric layers.
U.S. Pat. No. 4,479,100 relates to an impedance matching network which includes a plurality of electrodes of different cross-sectional areas. The electrodes are connectable in parallel with a major electrode to provide a selected desired capacitance.
U.S. Pat. No. 4,074,340 discloses a MLC which includes adjusting electrodes extending to side surfaces of the monolith. Capacitance adjustment is effected by externally connecting or disconnecting the adjusting electrodes with the major electrodes.
U.S. Pat. Nos. 4,048,593 and 2,758,256 disclose the concept of providing a multiplicity of discrete capacitors formed on a single substrate.